Conversion and separation of the constituents of organic mixtures containing both fatty and resin acids, particularly tall oil



Patented July 7, 1942 azsasic CONVERSION AND SEPARATION OF THECONSTITUENTS OF ORGANIC MIXTURES CONTAINING BOTH FATTY AND RESIN ACIDS,PARTICULARLY TALL OIL Frederick H. Gayer and Charles E. Fawkes, Chicago,Ill., asslgnors to Continental Research Corporation, Chicago Heights,Ill., a corporaflable matter and coloring impurities.

by distillation at reduced pressure.

tion of Illinois No Drawing. ApplicationJuly 17, 1939, Serial No.284,917

15 Claims. (Cl. 260-915) This invention relates to a process for theseparation of the major constituents of organic mixtures or oilscontaining both fatty and resin acids and especially to the clean, sharpand economic separation of the fatty and resin acids from such mixturesor oils, and particularly from tall 011. A more particular feature ofour invention is the recovery of fatty and resin acids in the form oftheir commercially useful and valuable derivatives.

source.

thereof.

inally present.

due.

unsaponifiable matter.

great disadvantage.

tion of the fatty and resin acid portionof tall oil but obtain as aresult of that separation derivatives of fatty and resin acidsrespectively, commercially more valuable than either fatty or resinacids in themselves.

Numerous processes have been proposed relating to the separation of thecomponents of tall oil, and one such process is disclosed in ourco-pending application Serial No. 169,654, which deals By this process10 with the separation of the fatty and resin acids Tall oil is aby-product of sulphate pulp or by a process involving esterification ofthe fatty kraft paper manufacture and is composed preacids,neutralization of the resin acids with an ponderantly of fatty acids,resin acids, unsaponialkali metal base and separating the fatty acid Theunesters from the resin acid soaps by means comsaponiflable matter iscomposed of hydrocarbons 15 prising furfural and water, and whereby weand cyclic alcohols belonging to the group of I obtain as final productsfatty acid esters and after phytosterols of which tall oil is anunusually rich acidifying the resin acid soaps, the free resin acids.

In our co-pending applications Serial No. In distinction from ouraforementioned process 169,655 and No. 169,656 the latter now issued asw the present invention comprises esterification of Patent No.2,223,850, both filed October 18, 1937, the fatty acids, converting theresin acids into we have disclosed processes for the refining of theirzinc salts and separating the fatty acid crude tall 011 and obtainingvaluable by-products esters from the zinc resinates.

According to those applications we rewe obtain high grade fatty acidesters and zinc move the coloring substances from crude tall oilresinates, both products of considerably greater and recover thecommercially valuable phytoscommercial value than either tall oil orfatty and terol in a substantially quantitative yield and resin acids inthemselves. obtain a refined oil of light color and containing In thepresent process, as in Serial No. 169,654, only afraction of theunsaponiflable matter origwe have taken advantage of the fact that theCrude tall oil also can be refined fatty acids in tall oil may-bereadily esterified with A greater monohydricaliphatic alcohols, such asmethyl-,

portion of the fatty and resin acids and of the ethylor higher alcohols,whereas, given the unsaponifiable matter distill over, the coloringproper conditions, the resin acids remain unmatter and phytosterolremaining in the still resi changed. This known chemical principle hasThe tall oils refined by distillation are also 30 been made the basis ofa new and useful process of of a considerably lighter color than thecrude oil separation and is an integral part thereof, as and also areessentially mixtures of fatty and hereinafter set forth. That is, theessence of this resin acids with a rather high proportion of inventionresides in taking together the old process of selective esterificationof the fatty acid Relatively little use has been made so far of 40components carried out under controlled and either crude or refined talloil, as the simultanespecified conditions in combination with thenew ouspresence of both fatty and resin acids is of step of converting theresin acids into their zinc These components in themsalts and separatingthe fatty acid esters from the selves, however, as fatty and resin acidsrespec- 43 zinc resinate by one of several possible methods.

tively are of great commercial importance. A large number of usefulcompounds are derived from these acids and find innumerable industrialapplications. A process which effects a sharp separation of thecomponents of tall oil is, there- ,fore, of great commercial value,especially in view forth we not only effect a clean and sharp separa-The first step of our process contemplates the esterification of thefatty acids contained in tall oil, which may be effected by severalmethods, such as refluxing or otherwise reacting the tall oil with amonohydric alcohol, such as methylor ethyl alcohol, or a highermonohydric alcohol. The alcohol is preferably used in excess over thatrequired for the quantitative esteriflcation of the fatty acids.Esterificatlon can be effected at or below the boiling point of thealcohol used in the presence of catalysts, such as, for example,sulphuric acid, or by any other conventional or suitable method. Weprefer the esterlfication method disclosed in our copending applicationSerial No. 284,975, filed July 17, 1939, whereby esterification iseffected in the absence of a catalyst at higher than atmosphericpressure. Esterification according to this method produces a mixture offatty acid esters, resin acids, unsaponifiable matter, excess alcoholand the water formed in the esterification reaction. We have found thatif We add to such a mixture zinc oxide in a quantity equivalent to theresin acids present, the resin acids are quantitatively converted intotheir zinc salts. On distilling off the excess alcohol and the waterformed first in the esterifilca- 1 tion reaction and second in' thereaction of the resin acids with zinc oxide, we obtain a mixture offatty acid esters and zinc resinates as a mobile liquid of substantiallythe same color as the original tall oil.

The transformation of the resin acids contained in the esterifiedmixture into their zinc salts can also be effected in other ways. Forexample, in one modification we first distill off the excess alcohol andthe water from the mixture obtained after esterification of the fattyacids and react the esterified oil so obtained with zinc oxide at arelatively low temperature, for example 100 C.

Another modification of our process consists in neutralizing the resinacids contained in the esterified oil with an alkali metal base, forinstance, sodium hydroxide and converting the alkali resinates into zincresinates by reacting them with the required amount of a solution of azinc salt, such as zinc chloride or zinc sulphate. The zinc resinatesformed dissolve into the fatty acid esters and we obtain the same liquidmixture as by reacting the esterified mixture directly with zinc oxide.

Of all these procedures we prefer the first one; namely, reacting theesterified mixture with zinc oxide before removing the excess alcohol.This procedure has a number of advantages, such as, (1) the presence ofalcohol vapors above the surface of the mixture precludes thepossibility of discoloration by contact with air, (2) convectioncurrents in the low boiling mixture keep the powdered zinc oxide insuspension, eliminating the necessity of stirring (3) the excess alcoholtakes up the water formed in the reaction of the resin acids with zincoxide and also counteracts the tendency for a possible hydrolysis of thefatty acid esters which is promoted by zinc oxide, (4) due to the lowboiling point of the mixture, which is only slightly higher than theboiling point of the alcohol used, pyrolytic changes do not occur.

The final step in our process consists in the separation of the fattyacid esters from the zinc resinates. We have found that this separationcan be achieved by two entirely difierent meth ods. We have discoveredthat if a mixture of fatty acid esters and zinc resinates is distilledat a reduced pressure, such as for example a pressure of 2050 mm. Hg.and at a temperature of about 180240 C. the fatty acid esters willdistill, whereas, under the same conditions, the zinc resinates arenon-volatile and will remain in the still as residue.

Due to the peculiar character of the resin acids, the distillation ofthe ester-zinc resinate mixture is often complicated by a solidificationor livering" of the zinc resinates in the first stages of heating. Wehave found that if the heating is continued the solidified white andquasi-crystalline zinc resinates become liquid again and dissolve in theesters which then can be distilled off, leaving a residue of clear,amorphous zinc resinate of resinous fracture and high melting point.

An alternative method for the separation of fatty acid esters from zincresinates is based on extraction with solvents which dissolve the fattyacid esters but are substantially non-solvents for the zinc resinates,such as low molecular weight, aliphatic alcohols, for example, methyl-,ethylor isopropyl alcohol. For instance, methyl alcohol, which atordinary temperatures is a poor solvent for the fatty acid esters oftall oil, becomes miscible in all proportions with these esters if thetemperature is raised above the critical solution temperature, which inthis case is 33 C. It has, however, substantially no solvent power forthe zinc resinates and only sucha quantity of zinc resinates will bedissolved as will be carried along with the esters. Decreasing theconcentration of the.esters in the solvent by using large quantities ofthe latter, for example about five volumes of solvent to one volume ofthe ester-zinc resinate mixture, will also decrease the total quantityof zinc resinate carried over into the ester solution. By this method weobtain zinc resinates substantially free of esters, the esters, however,are, as a rule, contaminated by small quantities of zinc resinates.After removing the solvent by distillation, we subject, therefore, theester extract to a distillation at reduced pressure and obtain a highgrade of pure fatty acid esters and a small quantity of zinc resinatesas still residue.

As starting material for our process we prefer I Four and one-halfkilograms of refined tall oil are esterified with methyl alcohol untilthe acid number becomes constant at a figure of 65. cor responding tothirty-five percent resin acids calculated as abietic acid. To thecooled mixture one hundred and sixty grams of zinc oxide, having aparticle size of less than two microns, are added and the mixturerefluxed until the zinc oxide is dissolved. Distillation of the excessmethyl alcohol and the water formed leaves 4.84

kilograms of a liquid residue of substantially the same color as therefined tall oil.

Example II Three hundred grams of the ester-zinc resinate mixtureobtained in Example I are distilled under reduced pressure with carbondioxide as vapor carrier. We obtain one hundred fifty-four grams of paleyellow ester as distillate and one hundred sixteen grams of zincresinate or high melting point as residue.

Example III Five hundred grams of the ester-zinc resinate mixtureobtained in Example I are heated under reflux with 2500 cc. methylalcohol and the mixture left to settle at about 40 C. The clear methylalcohol-ester solution is decanted, the methyl alcohol distilled and theresidue subjected to distillation under reduced pressure. We obtain asdistillate two hundred seventy grams of pale yellow esters of asaponification value of one hundred eighty, and twenty-five grams oflight colored zinc resinate as residue. The residue left after theextraction with methyl alcohol is heated at about 100 C. under reducedpressure to drive off occluded methyl alcohol. We obtain one hundredsixty-five grams of reddish yellow zinc resinate.

We claim as our invention:

1. The process of separating fatty acids from resin acids contained intall oil, which comprises converting the fatty acids into their alkylesters. converting the resin acids into their zinc salts and separatingthe alkyl esters of the fatty acids from the zinc resinates.

2. The process of separating fatty acids from resin acids contained intall oil, which comprises converting the fatty acids into their alkylesters, converting the resin acids into their zinc salts and separatingthe alkyl esters of the fatty acids from the zinc resinates bydistillation.

3. The process of separating fatty acids from resin acids contained intall oil, which comprises converting the fatty acids into their alkylesters, converting the resin acids into their zinc salts and separatingthe alkyl esters of the fatty acids from the zinc resinates byextraction with a volatile solvent which is substantially a nonsolventfor zinc resinates.

4. The process of separating fatty acids from resin acids contained intall oil, which comprises converting the fatty acids into their alkylesters, reacting the resultant mixture with zinc oxide to convert theresin acids into their zinc salts and separating the alkyl esters ofthevfatty acids from the zinc salts.

5. The process of separating fatty acids from resin acids contained intall oil, which comprises converting the fatty acids into their alkylesters, reacting the resultant mixture in an alcoholic solvent with zincoxide to convert the resin acids into their zinc salts, removing thesolvent and separating the fatty acid esters from the zinc resinates.

6. The process of separating fatty acids from resin acids contained intall oil, comprising reacting the tall oil with a monohydric aliphaticalcohol to esterify the fatty acids, convertin the resin acids intotheir zinc salts and separating the fatty acid esters from the zincresinates.

'l. The process of separating fatty acids from resin acids contained intall oil, comprising reacting the tall oil with an excess of amonohydric aliphatic alcohol to esterify the fatty acids, reacting theresultant mixture with zinc oxide to convert the resin acids into theirzinc salts, removing the excess alcohol and the water formed, andseparating the fatty acid esters from the zinc resinates.

8. The process of separating fatty acids from resin acids contained intall oil, which comprises converting the fatty acids into their alkylesters, neutralizing the resin acids with aqueous alkali, reacting themixture with a solution of a zinc salt to convert the alkali resinatesinto zinc resinatesyremoving' the formed water and separating the fattyacid esters from the zinc resinates.

9. The process of separating tall oil into fatty acids and resin acids,which comprises converting the fatty acids into their alkyl esters,converting the resin acids into their zinc resinates and heating themixture until a portion of the zinc resinate precipitates, continuingheating until the precipitated zinc resinates dissolve again, anddistilling the fatty acid esters from the zinc resinates.

10. The process of separating tall oil into fatty acids and resin acids,which comprises converting the fatty acids into their alkyl esters,converting the resin acids into their zinc resinates and distilling thefatty acid esters from the zinc resinates while maintaining the mixtureunder a subatmospheric pressure.

11. The process of separating tall oil into fatty acids and resin acids,which comprises converting the fatty acids into their alkyl esters,converting the resin acids into their zinc resinates and extracting thefatty acid esters with a volatile solvent which is substantially anon-solvent for zinc resinates, removing the solvent and recovering thefatty acid esters.

12. The process of separating tall oil into fatty acids and resin acids,which comprises converting the fatty acids into their alkyl esters,converting the resin acids into their zinc resinates and extracting thefatty acid esters with a volatile solvent which is substantially anon-solvent for zinc resinates, removing the solvent and purifying thefatty'acid esters by distillation.

- 13. The process of separating tall oil into fatty acids and resinacids, which comprises converting the fatty acids into their alkylesters, converting the resin acids into their zinc resinates andextracting the fatty acid esters with a low molecular weight aliphaticalcohol at a temperature above their critical solution temperature,separating the fatty acid ester extract solution from the zincresinates, removing the solvent from the solution by distillation andrecovering the fatty acid esters.

14. In the process of separating tall oil into fatty acids and resinacids the step which comprises converting the tall oil into a mixture ofalkyl esters of fatty acidswith zinc resinates by esterifying first thefatty acids with a monohydric aliphatic alcohol and subsequentlyconverting the resin acids into zinc resinates. v

15. In the process of separating tall oil into fatty acids and resinacids the step which comprises converting the tall oil into asolution'of zinc resinates in alkyl esters of fatty acids by esterifyingfirst the fatty acids with a monohydric aliphatic alcohol andsubsequently converting the resin acids into zinc resinates.

' FREDERICK H. GAYER.

CHARLES E. FAWKES.

